Heater arrangement for indirectly heated cathodes



Aug. 30, '1932. H. L. CROWLEY HEATER ARRANGEMENT FOR INDIRECTLY HEATEDCATHODES Filed April 5, 195o -mvembofc Patented Aug. 30, 1932tlniransraras earner esame HENRY L. CROWLEY, OF WEST ORANGE, NEWJERSEY,`ASSIG-1\TOR T0 HENRY L. CRW'LEY & CO. INC., OF WEST ORANGE, NEWJERSEY, A CORPOB-ATN F NEE/tf JERSEY HEATER ABRANGEMENT FOR INDIRECTLYHEATEQ CATHODES Application filed April 5,

Y of the socalled twin hole insulator com-r monly employed in tubestructures of this nature with respect to the electron emissive elementemployed in connection therewith to reduce the amount of lapsed timebetween the ,time the vacuum tube is supplied with current and the timethe electron emissive element becomes sufficiently active.

Other objects of the invention will appear more fully hereinafter. Theinvention consists substantiallyin the construction, corn- Z'O'binationand relative arrangement of parts all as will be more fully hereinafterset forth as shown in the accompanying drawing and finally pointed outin the appended claims.

Referring to the drawing:

Figure lis a view in perspective of an electron emissive and insulatorelement embodying my invention;

fldig. 2 is a longitudinal sectional view there- 0 s Fig. 3 is a similarview of a slightly modified character.

Y Similar reference characters refer to similar parts throughout theseveral views of the Y, Y drawing.

It is among the special purposes of my present invention to provide anarrangement of a twin hole insulator with respect to the electronemissive element employed in indi rectly heated cathode tube structuresin radio "receivers where current supply is ordinarily obtained from analternating current source such as electric lighting means. It is wellknown that in tube structures of this type a considerable amountof timeelapses between the time the switch of the radio receiver is turned onand the time the tubes become active. ThisV is due to the fact that theelectron emissive element must be heated to a required degree before thetube is operative. The required heat for the electron emissive element1930. serial No. 441,743.

is secured from the incandescent filament of the tube which is usuallyof the hairpin type, the respective legs of which are, of necessity,positioned in the respective holes of a socalledV twin hole insulator. thas been the common practice to provide the electron emissive element,sometimes known as a shield, in the form of a cylinder suitably coatedwith the electron emissive material. Inside of this cylinder and usuallyin closed contact therewith is positioned the twin hole insulatorthrough the two holes of which the filament ext-ends. By means of thisarrangement the filament when lighted must first heat the insulator andthereafter the heat by conduction is imparted to the electron emissiveelement to render the same operative. The life and efficiency of a `tubeis largely dependent upon thefsurface area of the electron emissiveelement.y Therefore, it is desirable to have the` samen as large as thestructural design of the tube willpermit. It is, of course, obvious thatthe larger the insulator the longer time will be required to e'ect heattransfer from the filament to the electron emissive element. For thesereasons a mean size has usually been adopted in which, however, maximumsurface `area of electron emissive material is in no sense utilizednotwithstanding its obvious advantages. l

It' is among the special purposes of my invention therefore to provide astructural arrangement of the insulator and electron emissive elementwhich will permit a maximum surface area of electron emissive materialLand a minimum diameter of twin hole or other type of insulator therebyincreasing the eficiency of the tube and reducing the inactive period ofthe tube after current is supplied thereto.V

Referring to the drawing the reference numeral l designates theinsulator which is shown as of the twin hole type and through which theholes 2 and 3 extend. lThe electron emissive shield, as is usual,surrounds the insulator but instead of being in close Contact therewithas heretofore employed, it is made of vany desired diametenlimited onlyby the dimensional design of the tube. Either one or both ends of theshield is bent9 drawn or v.otherwise formed inwardly so that the innerlike member and engaging the outer periph-y -V circumference thereof isin rigid supporting ery ofv said insulator. l

In testimony whereofl I have hereunto set contact with the end of theinsulator l. i 'Ihe shield which `is numbered 4 on the drawing hasformed thereon or therein the electronmy hand on thi emissive materialin the usual .Well knownv way. Gbviously, by increasing the diameter ofthe shield 4L but retaining the diameter of the insulator l constant anydesired surface marea of electron emissive'material may be secured'.This structure not only gives the insulator its necessaryrigidity ofsupport but in addition to effecting the heating of the f shield 4: byradiation from the insulator to l5 the shield throughout its lengthintermediate its ends it also effects a heating of theA` 1 shield byconduction because of the ContactV between the shield land the insulatorat its respective ends; VThus heating by conduction as well asby'radiation is effected with; the minimum amount of insulationnecessary to be heated vwithout limit other than the struc- .i

tural design of the tube as to the amount of electron emissive surfaceavailable.

ifv desired, the intermediate or body portion of the shield may beformed in one piece as Y shown in Fig. 3 and the end portions thereof, Ydesignated 5 on the drawing, may be welded,

' braised or otherwise secured thereto.

y y Many modifications'and changes in detail will-readily occur to thoseskilled in theart withoutdeparting from the spirit and scope 735;of myinvention. For example, I dovnot de-f sire' tobe limited to anyparticular type or c style of shield or electronemissive member,

nor do I desire ,to be ylimited or restricted to As showin Fig. 2 theShields@ with its reduced ends may be formed in one piece or,

any particular -type,styleor material of in- 49-sulation, or whether itbe of the twin hole i type or ofsome other'type, but have now set forththe objects and nature of my inventionY `and having shown andl describedstructures embodying the principles thereof whatIV fv-lclaim as newanduseful and of my'own in'- Y 'to secure by Letters Pat- Yinsulator'rodpositioned within said sleeve,

saidsleeve being of reduced diameterfatits' ends and fitting lclosely tothe said rod wherebysaid sleeve is held in spaced relation to said rodthroughout the greater portion of its length, and alongitudinal borethrough said rod to receive a heater 4Wire.

2. The combination Awith a sleeve-like elecn tron'emissive element, ofatwin hole insuc 60 lator kpositioned therein, and means for sup-y'porting thel ends of saidvtwin hole insulatorvv by Contact with theends of said element but i out of contact throughout the remainder vofthe length jtliereof, comprising inwardly l 765e tapered end portionsattached to said sleeves 3rd dayk of April A. D., 1930.

HENRY L. CROWLEY.

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